The Real Housewives of Orange County star tells ET her daughter has been sick for months, and no one can figure out what’s wrong with her. Vicki says Briana contracted the illness after she underwent surgery in Oklahoma.

“I flew there at night, picked her up in Oklahoma and drove her across the country to get her to California,” Vicki recalls. “We went immediately into the hospital. She was admitted three weeks in isolation. She had a cross-contamination, hospital-acquired infection from a hospital in Oklahoma. Very, very sick.”

Viewers got to see that trip on Monday night’s episode of the Bravo series. The preview for next week’s episode teased Briana in an ambulance, Vicki in tears while watching it drive away.

“She still is having residual effects from doctor's error in Oklahoma,” the star alleges. ”They were going to kill my daughter, basically. So, I got her out of there.”

"Two things: you don't mess with my family, you don't mess with my money,” Vicki warns. “My family is my everything, and I'm gonna find this doctor. He was going to kill my daughter. So, when I do find him, I'll probably pull him up against a wall and tell him what I think of him ... I want to go on a witch hunt for him."

“Beyond that, she has enlarged lymph nodes all over her body,” the Bravo star reveals. “We're trying to find answers. She just had a PET scan. We're still in the unknown stage. But she's sick.”

“She hasn't been released to go back to work yet,” Vicki adds. “It's been seven months … she's sick, but she's alive, and she's here, and we're gonna find out what it is. She's in the best hands right here [in Orange County].”

There is a silver lining here: Briana moving back to Orange County for treatment has made her and Vicki’s mother-daughter bond stronger.

“I got my daughter back,” Vicki beams. “That was answered prayers, because I prayed for that day where she said, 'I'm coming back home.' And if [my ex-boyfriend] Brooks [Ayers] was still in my life, she wouldn't have come back home. So, I gained so much by having Brooks and I not together.”

“Briana and I have wine together at night, and we talk together at night,” Vicki shares. “She's like, 'Mom! The kids are down, let's have some wine.' So, we watch a movie, and we talk, and it is... I am so much at peace, because that's all I ever wanted, was for her to say, 'I'm moving back.'”

You can see how Briana’s health journey plays out every Monday night when The Real Housewives of Orange County airs on Bravo at 9 p.m. ET. For more of our chat with Vicki, check out the video below.